Android中使用ArrayAdapter创建列表

Question

我是新手，解释一下事情的工作原理会非常有用。

所以我有这门课

        static class ListAdapter extends ArrayAdapter<String>{
            List<String> elements;
            Context context;

            public ListAdapter(Context context, List<String> elements) {
                super(context, 0, elements);
                this.context = context;
                this.elements = elements;
            }


            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                if (convertView == null) {
                    convertView = LayoutInflater.from(context).inflate(R.layout.list_item_ex, null, false);
                }

                TextView tvTitle = convertView.findViewById(R.id.tv_title);
                TextView tvDescription = convertView.findViewById(R.id.tv_description);
                ImageView ivExample = convertView.findViewById(R.id.iv_image);

                ivExample.setImageResource(R.drawable.offer_1);
                tvTitle.setText(elements.get(position));
                tvDescription.setText(String.valueOf(position));

                return convertView;
            }
        }

我在 MainActivity 中向列表中添加了一些元素以查看其工作原理，但我很难理解如何添加元素，每个元素都有不同的图片、描述等。

Answer 1

为此，您必须使用自定义类创建 ArrayAdapter： 以下是您必须遵循的步骤：

1. 创建自定义类

   public class Custom {
   int image;
   String title;
   String description;
   //constructeur 
   //getters and setters }
   

2. 创建适配器扩展 ArrayAdapter

   public class CustomArrayAdapter extends ArrayAdapter<Custom> {
   
   ArrayList<Custom> list;
   
       public CustomArrayAdapter(Context context, ArrayList<Custom> list) {
       super(context, R.layout.list_item_ex, list);this.list = list;
   }
   
   
   @Override
   public View getView(int position, View convertView, ViewGroup parent) {
   
       Custom custom=getItem(position);
   
       if (convertView == null) {
           convertView = LayoutInflater.from(getContext()).inflate(R.layout.list_item_ex, parent, false);
       }
   
       TextView tvTitle = convertView.findViewById(R.id.tv_title);
       TextView tvDescription = convertView.findViewById(R.id.tv_description);
       ImageView ivExample = convertView.findViewById(R.id.iv_image);
   
       ivExample.setImageResource(custom.getImage());
       tvTitle.setText(custom.getTitle());
       tvDescription.setText(custom.getDescription());
   
       return convertView;
   }
   

   }

3. 填充一个 ArrayList 然后 listView.setAdapter(customArrayAdapter);

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
   
       ListView listView=(ListView) findViewById(R.id.listView) ;
       ArrayList<Custom> list=new ArrayList<>();
       list.add(new Custom(R.mipmap.ic_launcher,"title","desc"));
   
       CustomArrayAdapter customArrayAdapter=new CustomArrayAdapter(this,listView);
   
       listView.setAdapter(customArrayAdapter);}